Telephone-transmitter



(No Model.) l

H. P. PRATT` 8v L. 0. MGPHERSON.

'TELEPHONE TRANSMITTER.

tented'Ja,n .-1l, 18,87.

le a 1 UNTTEn STATES HARRY I?. PRATT,

TELEPHONE-TRANSMITTER.

ATnNT Tries,

OF JEFFERSON,

SPECIFICATION forming part of Letters Patent No. 355,838, dated January11, 1887.

Application flcdilnne '.iO, 1885. Serial No. 170,525.2. (No model.)

To all 111710712/ it may concern:

Be it known that we, HARRY l?. PRATT, of

the city otGhcago, and LnoN O. MoPnnRsom' of the township of Jefferson,in the county of Cook and State of Illinois, have invented certain newand useful Improvements in Telephone-Transmitters,`of which thefollowing is a specification.

Our invention relates to that class of tele- Ic phone-transmitterswherein a diaphragm imparts the varying movements of son nd-waves of thevoice to the contact-surfaces of opposing electrodes of an electriccircuit, and by changing or shifting the contact of said electrodes I5actuates the circuit to reproduce sounds in a receiving-instrument.

It has been found necessary in 'instruments of this class to providemeans for adjusting the initial static pressure upon the electrodes 2owith great care, in order to secure proper reciprocal action betweenthem under all conditions and reproduce in the receiving-instrument thesounds which fall upon the transmitting-instrument.

It is also important to provide means which will counteract or destroyvibrations extraneous to those produced by the action of the voicedirected against the diaphragm, as well 'as to A dampen and tone downharsh and concussive .3o sounds directed upon the diaphragm. Thevibrations of the walls of a building and variations in temperatureaffect such instruments and destroytheir delicacy of adjustment.

The object of our present invention is to 35 provide an instrument ofsimple construction which will in a great measure fullill the requirements above stated, and which shall be susceptible of great rangeand delicacy of adjustment.

The improvement consists, primarily, in suspending in rear of thediaphragm a free lever of novel construction provided with a weightadjustable thereon, to exert .the required initial static pressure uponthe electrodes without offering obstruction to theifree movement of thediaphragm and electrodes.

The improvement consists, secondly, in a free lever suspended in rear ofthe diaphragm to bear upon a resiliently-supported electrode 5o arrangedupon one side of said free lever and a weightadjustably secured upon theopposite side of said lever to variably dampen the vibrations of thediaphragn'n.

The improvement consists, thirdly, in supporting one or both of thecarbon electrodes in an elastic socket or upon an elastic bed,preferably of soft rubber, to afford a yielding contact for theelectrodes.

In the accompanying drawings, Figure lis a view in elevation of the rearside ofthe cover `6o of a telephone-transmitter fitted with yourimprovements; Fig-2, a vertical section in the line x x ofy Fig. 1,showing a simple form of free lever and adjustable weight for supportingthe electrode; Fig. 3, a similar view showing a strip of spring. metalarranged between the diaphragm and free lever'l for suspending one ofthe electrodes upon a resilient support or holder; Fig; 4, a likerepresentation of a further modification of the device, wherein 7ocompound free levers are employed and an elastic cushion is arrangedbetween the levers; and Fig. 5, a sectional detail of the lower end ofthe free leverprovided with an elastic socket for the electrodes, aswill hereinafter appear.

The cover A of the telephone-box supports a diaphragm, B, Iin anywell-known or preferred manner. In this instance a peripheralring ofrubber, C, is arranged between the rim of the diaphragm and the innerside of the 8o box-cover, and the diaphragm is held in place oppositetheaperture ein said cover by means of screws b and metal clips b',provided with rubber pads b2, which bear upon the rim of the diaphragm.

The diaphragm is provided with an elec? trode, F, in this instance ofplatinum wire arranged centrally thereto, againstwhich is supported acarbon electrode in the Afollowing manner: A bracket or pivot-post, D,is se- 9o cured to the inner side of the box-cover above the diaphragm,and supports a free lever, E, pivoted thereto at its upper end, andsuspended to extend radially'to the central portion of the diaphragm.The lower end ofthe 95 free lever E is enlarged and recessed to receivea carbon electrode, F', and the upper end of said lever is formed withan elbow, e, through the outer end of which the pivot-pin e'passes.

As the free lever is suspended from a point Ico outside of a linepassing centrally and longitudinally through it, the lever would rest inits otherwise acted upon.

2o upon the free'lever.

io trodes in the following manner:

An arm, E', is screwed into the free lever to project rearwardlytherefrom, and is screwxthreaded to receive a weight, G, made adjust-Aable thereon. The weight G may be placed I5 upon the inner end ofthe armE immediately beneath the pivotpin, where its power upon vthe leverwould not be exerted, or it maybe placed upon the outer end ofthe lever,to exert a much more than counterbalancing effect Vith this range ofadjustment in either direction any varying condition or requirement ofadjustment may be complied with.

Both of the electrodes may be of carbon, if preferred, and may beconnected with the linewires HH iu the'usual way. One ofthe electrodes,F, may be connected to the diaphragm in any wellknown manner, as shownin Figs. 2 and 4, or it may be suspended upon 3o a strip of springmetal, I, secured at its upper end to a post, fi, on the cover, and heldat its lower end between tbe lips of a metal holder, I, screwed to thecover, as shown in Fig. 3, which will admit ofthe free resilientmovement of the spring.

The electrode F will iu the arrangement thus described partake of asecondary vibration from the diaphragm and .be held to closely followits movements by the pressure of the 4o Weight in one direction and theresilient action of the spring in the other direction. The line-wires HH areconnected in this instance, respectively, tothe upper end of theelectrodeholder l' and to the upper end of the free lever-E. A verysimple a'nd highly-sensitive mode of applying a free lever with an adjustable weight and resilient electrodeholder is illustrated in Fig. 4,wherein two free levers, E2 E3, are suspended from a post, D, to swing5o alongside of each other in rear of the diaphragm.

A soft-rubber button, K, is secured to one of the levers to bear againstthe other and afford an elastic bed or cushion between said levers,

which will eii'ectually absorber dissipate any jarring vibrations whichmay be imparted to the levers and diaphragm.

The weight may be delicately adjusted upon the arm ot the lever tocompensate for the 6o proper degree of resiliency required in the springor cushion, and thus accurately counterbalance the forces operating uponeach other to secure the most sensitive responses to the vibrations ofthe diaphragm. When two levers are suspended to act one uponthe other,

as above described, the jarring vibrations incident to freely-suspendedor pendulous bodies, derived from forces other than the voice actingupon the diaphragm, will serve to partially l is bored through toreceive a metal cup-pin,

L, secured thereon by a nut, L', and recessed in its enlarged or headedportion to receive the carbon.

A softrubber sleeve, L2, formed with a flanged head, l, is securedaround the pin L, and between it and the bore of the free lever, whichprovides an elastic seat or socketv for the carbon-holder and permitsthe carbon electrode to adapt itself closely. at all times to itsopposing electrode and yield to any rubbing or frictional pressureexerted upon it.

In conclusion, it may be remarked that the electrodes herein referred tomay be made of any substance, material,or composition ofmatter ofsuitable conductivity.. Y

We claim as our invention and desire to secure by Letters Patent- 4 l.In atelephone-transmitter, the combination, with the diaphragm, of theelectrodes, a

spring-actuated or elastic electrodeholder, an

adjustable depending lever pivoted at one end to a bracket on thecasing, a screw-threaded rod connected to said lever below its pivotalpoint and extending outwardly in a plane at right angles thereto, and aweight adjustably mounted on saidrod, whereby a compensating pressureagainst the resiliency of the electrode-holder may be given,substantially as described.

2. In a telephone-transmitter, a cushioned electrode-support consistingof a metallic pin having a cup formed on one end for holding theelectrode, and a screw-thread on its other end engaged by a nut, and anelastic cushion surrounding said pin and resting under the cup-shapedportion thereof, substantially as Witnesses:

WM. H. ROWE, CrrAsG. PAGE.

IIS

